Axle assembly for low floor vehicle

ABSTRACT

An axle assembly for a low floor vehicle is described herein. The axle assembly includes an axle housing and a drive unit for driving a wheel assembly. The axle housing including a first gearbox, a second gearbox and a cradle assembly coupling the first gear box to the second gear box. The axle assembly includes first and second hub assemblies that form a first axis of rotation. The first gearbox includes an electric motor that is coupled to a transmission used to rotate an output shaft. The first gearbox also includes a differential mounted for rotation with the transmission and a first drop box mounted for rotation with the differential. The axle assembly also includes a portal axle mounted for rotation with the first drop box and extends from the first gearbox to the second gearbox wherein the portal axle forms a second axis of rotation that is offset from the first axis of rotation of the hub assemblies. The second gearbox includes a second drop box mounted for rotation with the portal axle and is adapted to drive the second hub assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the U.S. national phase of PCT/US2019/031786, filedon May 10, 2019, which claims the benefit of priority to U.S.Provisional Application No. 62/669,743, filed May 10, 2018. Thedisclosures set forth in the above-referenced applications areincorporated herein by reference in their entireties.

BACKGROUND

In order to aid ingress and egress, it is desirable for a motor vehicleto have a floor that is as low to the ground as possible. Busses andpeople carriers, commonly called low floor vehicles, are examples ofvehicles that benefit from a low floor height. By minimizing the floorheight, a step at a door of the vehicle may be eliminated, which in turnallows easier ingress and egress for vehicle passengers. Elimination ofsteps is especially beneficial to disabled passengers, and passengerscarrying items, such as strollers. Increasingly, manufacturers haveturned to electric and hybrid propulsion systems for low floor vehiclesfor increased performance and efficiency. In order to have the floor ofthe vehicle as low as possible, the drivetrain components are relocatedso as to reduce intrusions into the vehicle floor.

SUMMARY

Accordingly, the present disclosure provides an axle assembly for a lowfloor vehicle with increased performance and efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present disclosure will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings.

FIG. 1 is a perspective view of an axle assembly for a low floorvehicle;

FIG. 2 is an elevation view of an axle assembly for a low floor vehicle;

FIG. 3 is a cutaway perspective view of a drive unit for an axleassembly for a low floor vehicle;

FIG. 4A is a cross-sectional view of the drive unit of FIG. 3 shown in afirst reduction ratio;

FIG. 4B is a cross-sectional view of the drive unit of FIG. 3 shown in asecond reduction ratio;

FIGS. 5-8 are perspective views of the axle assembly for a low floorvehicle shown in FIG. 1, according to embodiments of the presentdisclosure;

FIG. 9 is an elevation view of a rear portion of the axle assembly shownin FIGS. 5-8;

FIG. 10 is an elevation view of a left side of the axle assembly shownin FIGS. 5-8;

FIG. 11 is an elevation view of a right side of the axle assembly shownin FIGS. 5-8;

FIG. 12 is a top view of the axle assembly shown in FIGS. 5-8;

FIG. 13 is a bottom view of the axle assembly shown in FIGS. 5-8;

FIGS. 14 and 15 are perspective views of the axle assembly shown inFIGS. 5-8;

FIG. 16 is a top view of the axle assembly shown in FIG. 15;

FIG. 17 is an elevation view of a rear portion of the axle assemblyshown in FIG. 15;

FIG. 18 is an elevation view of a left side of the axle assembly shownin FIG. 15;

FIGS. 19 and 20 are perspective views of a cradle assembly that may beused with the axle assembly shown in FIGS. 5-8, according to embodimentsof the present disclosure;

FIGS. 21 and 22 are perspective views of a portion of the cradleassembly shown in FIGS. 19 and 20;

FIG. 23 is an elevation view of a front portion of the cradle assemblyshown in FIG. 21;

FIG. 24 is an elevation view of a right side of the cradle assemblyshown in FIG. 21;

FIG. 25 is a top view of the cradle assembly shown in FIG. 21;

FIG. 26 is a bottom view of the cradle assembly shown in FIG. 21;

FIG. 27 is a perspective view of a top cover that may be used with thecradle assembly shown in FIGS. 19 and 20;

FIG. 28 is a view of a top surface of the top cover shown in FIG. 27;

FIG. 29 is a side view of the top cover shown in FIG. 27;

FIG. 30 is a view of a bottom surface of the top cover shown in FIG. 27;

FIG. 31 is a perspective view of a bottom cover that may be used withthe cradle assembly shown in FIGS. 19 and 20;

FIG. 32 is a view of a top surface of the bottom cover shown in FIG. 31;

FIG. 33 is a side view of the bottom cover shown in FIG. 31;

FIG. 34 is a view of a bottom surface of the bottom cover shown in FIG.31;

FIGS. 35 and 36 are perspective views of a gearbox that may be used withthe axle assembly shown in FIGS. 5-8, according to embodiments of thepresent disclosure;

FIG. 37 is a perspective view of a gearbox housing that may be used withthe gearbox shown in FIGS. 35 and 36;

FIG. 38 is an elevation view of a front-side portion of the gearboxhousing shown in FIG. 37;

FIG. 39 is an elevation view of a back-side portion of the gearboxhousing shown in FIG. 37;

FIG. 40 is a top view of the gearbox housing shown in FIG. 37;

FIG. 41 is a bottom view of the gearbox housing shown in FIG. 37;

FIGS. 42 and 43 are side views of the gearbox housing shown in FIG. 37;

FIG. 44 is a perspective view of a gearbox cover that may be used withthe gearbox shown in FIGS. 35 and 36;

FIG. 45 is a top view of the gearbox cover shown in FIG. 44;

FIG. 46 is a side view of the gearbox cover shown in FIG. 44;

FIG. 47 is a bottom view of the gearbox cover shown in FIG. 44;

FIG. 48 is another cutaway perspective view of the drive unit for anaxle assembly for a low floor vehicle;

FIGS. 49-52 are cross-sectional views of the drive unit shown in FIG.48, according to an embodiment of the present disclosure;

FIG. 53 is a cutaway perspective view of the drive unit shown in FIG.48;

FIG. 54 is a sectional view of the drive unit of FIG. 53;

FIG. 55 is a block diagram of axle assembly shown in FIGS. 5-8;

FIG. 56 is another perspective view of the axle assembly for a low floorvehicle shown in FIG. 1, according to embodiments of the presentdisclosure;

FIG. 57 is a top view of axle assembly shown in FIG. 56;

FIG. 58 is a bottom view of the axle assembly shown in FIG. 56;

FIG. 59 is a front view of the axle assembly shown in FIG. 56;

FIG. 60 is a rear view of the axle assembly shown in FIG. 56;

FIG. 61 is a right side view of the axle assembly shown in FIG. 56;

FIG. 62 is a left side view of the axle assembly shown in FIG. 56;

FIG. 63 is a perspective view of the cradle assembly shown in FIG. 56;

FIG. 64 is a top view of the cradle assembly shown in FIG. 63;

FIG. 65 is another top view of the cradle assembly shown in FIG. 63;

FIG. 66 is bottom view of the cradle assembly shown in FIG. 63;

FIG. 67 is front view of the cradle assembly shown in FIG. 63;

FIG. 68 is rear view of the cradle assembly shown in FIG. 63;

FIGS. 69 and 70 are side views of the cradle assembly shown in FIG. 63;

FIG. 71 is a perspective view of the gearbox assembly shown in FIG. 56;

FIG. 72 is a front view of the gearbox housing shown in FIG. 56;

FIG. 73 is a rear view of the gearbox housing shown in FIG. 56;

FIG. 74 is a top view of the gearbox housing shown in FIG. 56;

FIG. 75 is a bottom view of the gearbox housing shown in FIG. 56;

FIGS. 76 and 77 are side views of the gearbox housing shown in FIG. 56;

FIG. 78 is another perspective view of the gearbox assembly shown inFIG. 56;

FIG. 79 is an elevation view of an axle assembly for a low floorvehicle, according to another embodiment of the present disclosure;

FIGS. 80-83 are schematic diagrams of the axle assembly of FIG. 79,according to embodiments of the present disclosure; and

FIGS. 84-94 are perspective views of the wheel drive unit including anelectric motor, a transmission and a hub assembly.

DETAILED DESCRIPTION

With reference to the figures, wherein like numerals indicate like partsthroughout the several views, an axle assembly 10 for a low floorvehicle is shown in FIGS. 1 and 2. The axle assembly 10 includes an axlehousing 12 having a bridge section 14 and outer sections 16 arranged atopposite ends of the bridge section 14. Each outer section 16 is spacedlaterally from the other relative to the vehicle. The axle assembly 10further includes mounts 18 coupled to the axle housing 12, which may beused to attach the axle assembly 10 to the vehicle. Additionally,suspension control arms 20 may be coupled to the mounts 18 to movablyattach the axle assembly 10 to the vehicle. The vehicle may be anelectric vehicle or a hybrid vehicle with an electric motor and internalcombustion generator/motor. Advantageously, the mounts 18 may beconfigured to allow the axle assembly 10 to be retrofitted into anexisting vehicle. For example, a low floor bus originally equipped witha traditional axle assembly may be upgraded to include the axle assembly10 in place of the traditional axle assembly.

A wheel 22 is coupled to each end of the axle assembly 10 to support thevehicle and transfer motive power to a road surface, as shown, forexample, in FIGS. 1 and 2. In the embodiment shown, the axle assembly 10is a dual wheel configuration with a pair of wheels 22 coupled to eachend of the axle assembly 10. Each wheel 22 defines an axis of rotation24. The axis of rotation 24 of each wheel 22 is generally aligned.

The axle assembly 10 further includes a wheel drive unit 26 housedwithin each outer section 16 of the axle housing 12, as shown in FIGS.3, 4 a and 4 b. Each of the wheel drive units 26 is configured tooperate independently of the other drive unit 26 so the wheels onopposite sides of the axle can rotate independently of the other side.Each wheel drive unit 26 may operate at a different speed during aturning maneuver of the vehicle, or in response to available traction ateach wheel 22. Each wheel drive unit 26 includes an electric motor 28, atransmission 30, and a hub assembly 32 for mounting one or more wheels22. The axle housing 12 integrates the electric motor 28 andtransmission 30 compactly, increases cooling for heat dissipation, andsupports vehicle loads through the suspension control arms 20 and mounts18. The transmission 30 allows the vehicle to have an increased topspeed while operating more efficiently at low speeds.

As shown in FIG. 2, the bridge section 14 is arranged between each outersection 16 of the axle housing 12. It is desirable for a height of a lowfloor to be both as low as possible, and a width to be as wide aspossible in order to maximize capacity of the vehicle. As such, thebridge section 14 is offset from the axis of rotation 24 of the wheels22 in order to decrease the height of the low floor of the vehicle. Theouter sections 16 are configured to house the wheel drive units 26within the axle housing. Each outer section 16 has a width, which isdecreased in order to increase the width of the low floor of thevehicle. The bridge section 14 may be integrally formed with the outersections 16 or may be coupled to the outer sections 16 using methodscommonly used in the art. For example, the bridge section 14 may bewelded, pressed, or bolted to the outer sections 16. The bridge section14 may be hollow or solid.

The axle assembly 10 may further include a braking system for thevehicle. The braking system may include air cylinders, brake hoses,brake drums, brake rotors 35, brake calipers 37, and the like. In theembodiment shown, brake rotors 35 and brake calipers 37 are adjacent hubassembly 32.

Referring now to FIGS. 3-4B and 48-54, the wheel drive unit 26 is shownwith the axle housing 12 removed. The drive unit 26 includes an axleshaft 36 coupled to the transmission 30 and the hub assembly 32. Thetransmission 30 is coupled to both the electric motor 28 and the axleshaft 36, and the hub assembly 32 is coupled to the wheel 22. As such,torque generated by the electric motor 28 is transferred through thetransmission 30 to the hub assembly 32, and then to the wheel 22. Thedrive unit 26 further includes an elongated axle support 38 coupled tothe axle housing 12. The axle shaft 36 is disposed in the axle support38 between the hub assembly 32 and the transmission 30. As will bediscussed in further detail below, the transmission 30 has two reductionratios, which may be selectively engaged by an operator of the vehicle,or by use of a transmission controller.

The electric motor 28 generates torque to drive the wheels 22, as shownin FIGS. 4a, 4b and 48. The electric motor 28 includes a motor shaft 40that protrudes from the electric motor 28. A drive gear 42 is fixed tothe motor shaft 40. The motor shaft 40 defines a rotational axis 44 thatextends through the electric motor 28. The electric motor 28 may be a DCor AC motor, brushed or brushless, or other types of motors commonlyknown in the art. The electric motor 28 is oriented such that the motorshaft 40 protrudes away from the respective wheel 22 with the rotationalaxis 44 of the motor shaft 40 arranged parallel to the axis of rotation24 of the wheels 22. Relative to the vehicle, the electric motor 28 isspaced longitudinally from the axis of rotation 24 of the wheels 22.

By orienting the electric motor 28 such that the motor shaft 40protrudes away from, and is longitudinally spaced from the axis ofrotation 24 the respective wheel 22, packaging space within the outersections 16 of the axle housing 12 is conserved without the need toincrease the width of the outer sections 16, as shown in FIGS. 4a, 4b .The additional packaging space within the outer sections 16 allows thetransmission 30 to be arranged adjacent to the electric motor 28.Preferably, the overall width of the electric motor 28 is substantiallysimilar to the overall width of the transmission 30. As such, the widthof the outer sections 16 is not materially affected by the introductionof the electric motor 28. Stated another way, with the transmission 30arranged adjacent to the electric motor 28 the width of the low floormay be wider than if the transmission 30 was arranged otherwise.Furthermore, the increased packaging space within the outer sections 16allows for the transmission 30 to be configured with multiple reductionratios. Aligning each of the axes of rotation 24, 44 in a parallelmanner increases the efficiency of the transmission 30.

As mentioned above, the drive unit 26 includes the transmission 30, asshown in FIGS. 4a, 4b and 54. The transmission 30 has a first reductionratio and a second reduction ratio. The transmission 30 includes aninput idler shaft 46, an output shaft 48, and a shift mechanism 50. Theidler shaft 46 and the output shaft 48 each have two ends rotatablysupported by bearings 52 in the drive unit 26. A driven gear 54 is fixedto the idler shaft 46 and meshes with the drive gear 42. The driven gear54 transfers torque to the idler shaft 46 from the drive gear 42.

In addition to the driven gear 54, two idler gears 56, 58 are rotatablysupported on the idler shaft 46. A first idler gear 56 corresponds tothe first reduction ratio of the transmission 30, and a second idlergear 58 corresponds to the second reduction ratio of the transmission30. Each of the idler gears 56, 58 can spin freely on the idler shaft 46such that when the corresponding reduction ratio is not engaged, notorque is transferred between the idler shaft 46 and the idler gear 56,58. As will be discussed in further detail below, each idler gear 56, 58includes a splined portion engageable with the shift mechanism 50 torotatably couple the idler gear 56, 58 to the idler shaft 46.

The shift mechanism 50 of the transmission 30 includes a shift ring 60,a shift fork (not shown), and an actuator (not shown). The shift ring 60is slideable along the idler shaft 46 between the first idler gear 56and the second idler gear 58. The shift ring 60 is rotatably coupled tothe idler shaft 46 such that the shift ring 60 and the idler shaft 46rotate at the same speed. The shift ring 60 includes at least onesplined portion engageable with the splined portion of either of theidler gears 56, 58. Additionally, the shift ring 60 defines a groove 62configured to engage the shift fork.

The shift fork is coupled to the actuator and movable to select thefirst reduction ratio and the second reduction ratio. The shift fork isengaged with the shift ring 60 such that the shift fork is capable ofmoving the shift ring 60 into engagement with one of the idler gears 56,58. Additionally, the shift fork may be movable into a neutral positionwhere neither of the idler gears 56, 58 are engaged with the shift ring.The shift mechanism 50 may further include a synchronizer to aidshifting. The actuator may be controlled manually or automatically. Theactuator may be responsive to hydraulic pressure, pneumatic pressure, orelectronic signals generated by a transmission control module.Alternatively, the actuator may include a mechanical linkage controlledby the vehicle operator.

The transmission 30 further includes two output gears 64, 66, as shownin FIGS. 4a, 4b and 48. Each of the output gears 64, 66 is coupled tothe output shaft 48, a first output gear 64 engaged with the first idlergear 56, and a second output gear 66 engaged with the second idler gear58. The output gears 64, 66 are rotatably fixed to the output shaft 48such that the output gears 64, 66 and the output shaft 48 rotate at thesame speed. The output shaft 48 is formed to include a bore 49 that isconfigured to receive the axle shaft 36. Bore 49 may be splined or keyedsuch that the axle shaft 36 and the output shaft 48 rotate together. Asmentioned above, the axle shaft 36 is disposed in the axle support 38and coupled between the hub assembly 32 and the transmission 30.

The hub assembly 32 is arranged at an end of the axle support 38opposite the transmission 30, as shown in FIGS. 4a and 4b . The hubassembly 32 includes a wheel hub 68 having a wheel flange 70. The wheelhub 68 is rotatably supported on the axle support 38 by a pair of hubbearings 72. The wheels 22 may be secured to the wheel flange 70 usingbolts, nuts, and other fasteners known in the art.

Each hub assembly 32 further includes a planetary gear assembly 74,which increases torque to drive the wheels 22. The planetary gearassembly 74 includes a sun gear 76, a planet carrier 78, a plurality ofplanet gears 80, and a ring gear 82. The ring gear 82 is coupled to theaxle support 38. The sun gear 76 is coupled to the end of the axle shaft36 and disposed in the ring gear 82. The ring gear 82 is fixed relativeto the sun gear 76.

The plurality of planet gears 80 are rotatably coupled to the planetcarrier 78. The planet carrier 78 is arranged adjacent to the ring gear82 with each planet gear 80 disposed in the ring gear 82. Each planetgear 80 engages both the ring gear 82 and the sun gear 76. When the axleshaft 36 rotates the sun gear 76, the sun gear 76 rotates each planetgear 80, which in turn rotates the planet carrier 78. The planet carrier78 is coupled to the wheel hub 68 such that the planet carrier 78 andthe wheel hub 68 rotate at the same speed.

Referring specifically to FIG. 4A, the drive unit 26 is shown with thetransmission 30 in the first reduction ratio and a torque path showingtorque transfer through the drive unit 26. Torque generated by theelectric motor 28 rotates the drive gear 42. The drive gear 42 rotatesthe driven gear 54 coupled to the idler shaft 46. The idler shaft 46rotates the shift ring 60, which is engaged with the first idler gear56. The first idler gear 56 is engaged with the first output gear 64 totransfer rotation to the output shaft 48 and axle shaft 36. Rotation ofthe axle shaft 36 is further transferred through the planetary gearassembly 74 to the wheels 22.

Referring now to FIG. 4B, the drive unit 26 is shown with thetransmission 30 in the second reduction ratio and a torque path showingtorque transfer through the drive unit 26. Torque is generated in theelectric motor 28 to rotate the motor shaft 40 and the drive gear 42.The drive gear 42 rotates the driven gear 54 coupled to the idler shaft46. The idler shaft 46 rotates the shift ring 60, which is engaged withthe second idler gear 58. The second idler gear 58 is engaged with thesecond output gear 66 to transfer rotation to the output shaft 48 andaxle shaft 36. Rotation of the axle shaft 36 is further transferredthrough the planetary gear assembly 74 to the wheels 22.

In one embodiment, as shown in FIG. 55, the axle assembly 10 may includea first motor assembly 100 for driving a first wheel assembly 102, and asecond motor assembly 104 for driving a second wheel assembly 106. Eachmotor assembly 100 and 104 includes a drive unit 26, and inverter device108 coupled to the drive unit 26, and a controller 110 for operating theelectrical inverter device 108 and the drive unit 26. Each inverterdevice 108 is coupled to one or more batteries 112 for supplyingelectrical power to the inverter electrical inverter 108. Eachcontroller 110 is coupled to a VMU unit 114. In one embodiment, thefirst motor assembly 100 is configured to operate independently from thesecond motor assembly 104. In addition, each controller 110 isprogrammed to operate the corresponding motor assemblies at a variablespeed. For example, in one embodiment, the VMU 114 may be programmed totransmit signals to each controller 110 such that, during operation, thecontroller 110 of the first motor assembly 100 may operate the driveunit of the first motor assembly 100 at a first rotational speed, andthe controller 110 of the second motor assembly 100 may operate thedrive unit of the second motor assembly 104 at a second rotational speedthat is different than the first rotational speed of the first motorassembly 100. In addition, during operation, only one of the motorassemblies may be operated to drive the corresponding wheel assemblywith the other motor assembly allowing the corresponding wheel assemblyto spin freely. This provides the axle assembly 10 with the capabilityof not driving one of the electric motors when the load requirements arelow. This can be done through the controller that doesn't send power toone of the motors, or can be done mechanically to disconnect the motor.Disconnection can be through a neutral position as part of a speedchange mechanism, or through a clutch or the like. When in this mode,the axle assembly 10 operates to drive only one wheel on one side of thevehicle. For example, in a tandem axle configuration (four wheels), theaxle assembly 10 may operate to generate power that can be alternatedbetween different motors based on needs and loads.

Referring to FIGS. 5-78, of the illustrated embodiment, each outersection 16 includes a gearbox 116 that includes a gearbox housing 118and a gearbox cover 120. The bridge section 14 includes a cradleassembly 122 that is coupled to each gearbox housing 118. The cradleassembly 122 includes a cradle frame 124, a top cover 126 that isremovably coupled to a top portion 128 of the cradle frame 124, and abottom cover 130 that is removably coupled to a bottom portion 132 ofthe cradle frame 124. The cradle frame 124 includes an inner surface 134that defines a cavity 136 that extends through the cradle frame 124. Thetop cover 126 extends across the top portion 128 of the cradle frame 124and the bottom cover 130 extends across the bottom portion 132 of thecradle frame 124 to enclose the cavity 136 to form a cradle chamber 138.The cradle chamber 138 is sized and shaped to receive one or moreelectrical inverter devices 108 that are positioned within the cradlechamber 138.

The cradle frame 124 includes a forward member 140, a rear member 142, afirst side member 144 and an opposite second side member 146. The firstside member 144 and the second side member 146 extend along alongitudinal axis 148 and are spaced a distance apart along a transverseaxis 150 that is perpendicular to the longitudinal axis 148. In theillustrated embodiments, the transverse axis 150 is substantiallyparallel to the axis of rotation 24 of each wheel 22. The forward member140 is coupled between the first side member 144 and the second sidemember 146 to form a front portion 152 of the cradle frame 124. The rearmember 142 is coupled between the first side member 144 and the secondside member 146, and is spaced a distance from the forward member 140along the longitudinal axis 148 to form a rear portion 154 of the cradleframe 124.

The first side member 144 and the second side member 146 each includeone or more cable access openings 156 that extend through the sidemembers. The cable access opening 156 is sized and shaped to receive aplurality of electrical cables therethrough to allow electrical andcommunication cables to extend from the electrical inverter devices 108positioned within the cradle chamber 138 to an area outside the cradlechamber 138. The electrical and communication cables may include, butare not limited to, 3 phase cables, two DC cables, a motor connectioncable, and customer interface cable.

A pair of forward mounting flanges 158 extend outwardly from oppositeends of the forward member 140. Each forward mounting flange 158includes a mounting member 160 and a support arm 162 that is coupledbetween the mounting member 160 and the forward member 140. The mountingmember 160 is spaced a distance outwardly from an outer surface 164 of acorresponding side member 144, 146 as measured along the transverse axis150. The mounting member 160 includes a planar mounting surface 166 thatis configured to engage an outer surface of a corresponding gearboxhousing 118. The planar mounting surface 166 is orientated substantiallyparallel to the outer surface 164 of the corresponding side members 144,146.

Referring to FIGS. 23 and 24, of the illustrated embodiment, the forwardmember 140 includes a top surface 168 and a bottom surface 170, andincludes a height 172 measured between the top surface 168 and thebottom surface 170 along a vertical axis 174. The mounting member 160includes a bottom surface 176 and a top surface 178 and the planarmounting surface 166 extending between the bottom surface 176 and thetop surface 178. The planar mounting surface 166 includes a height 180measured between the top surface 178 and the bottom surface 176 of themounting member 160 along the vertical axis 174. The bottom surface 176of the mounting member 160 is substantially flush with the bottomsurface 170 of the forward member 140. The top surface 178 of themounting member 160 is spaced a vertical distance from the top surface168 of the forward member 140 such that the height 180 of the mountingsurface 166 is greater than the height 172 of the forward member 140. Aplurality of fastener openings 173 extending through the planar mountingsurface 166 of the mounting member 160. Each fastener opening 173 issized and shaped to receive a fastener such as, for example, a bolt tocouple the cradle frame 124 to the gearbox housing 118.

In addition, the support arm 162 includes an arcuate top surface 182that extends between the top surface 178 of the mounting member 160 andthe top surface 168 of the forward member 140. The support arm 162 alsoincludes an arcuate outer surface 184 and an arcuate inner surface 186.The arcuate inner surface 186 defines a gap 188 between the mountingmember 160 and a side member outer surface 164 of the corresponding sidemembers 144, 146. The gap 188 is sized and shaped to receive a portionof the gearbox housing 118 therein to facilitate coupling the cradleframe 124 to the gearbox housing 118.

Referring to FIGS. 12-26 and 63-70, of the illustrated embodiment, theforward member 140 also includes a suspension arm support assembly 190that extends outwardly from the outer surface of the forward member 140.The outer surface of the forward member 140 includes an arcuate shapethat defines a pair of slots 192 between opposing ends of the suspensionarm support assembly 190 and the forward member outer surface. Each slot192 is sized and shaped to receive an end of a suspension control arm20, and a mounting surface 194 is defined at each end of the suspensionsupport arm assembly 190 to facilitate coupling the suspension controlarm 20 to the suspension arm support assembly 190, as shown in FIG. 16.The forward member outer surface includes recessed portions 196 that arepositioned with respect to at each end of the suspension support armassembly 190. Each recessed portion 196 is sized and shaped to receivean end of a suspension arm 20 such that each suspension arm 20 extendsoutwardly from the forward member 140 at an oblique angle.

In the illustrated embodiment, a pair of rear mounting flanges 198extend outwardly from opposite ends of the rear member 142. Each rearmounting flange 198 includes a rear mounting member 200 and a rearsupport arm 202 that is coupled between the rear mounting member 200 andthe rear member 142. The rear mounting member 200 is spaced a distanceoutwardly from the corresponding side member outer surface 164 asmeasured along the transverse axis 150. The rear mounting member 200also includes a rear planar mounting surface 204 that is configured toengage an outer surface of a corresponding gearbox housing 118, and isorientated substantially parallel to the side member outer surface 164and the planar mounting surface 166 of the forward mounting member 160.

In the illustrated embodiment, the planar mounting surface 166 of theforward mounting member 160 and the rear planar mounting surface 204that are positioned on the same side of the cradle frame 124 areorientated within the same plane to facilitate coupling the cradleassembly 122 to the corresponding gearbox housing 118, as shown in FIGS.23 and 24. In addition, the rear planar mounting surface 204 includes aheight 206 measured along the vertical axis 174 that is substantiallysimilar to the height of the corresponding planar mounting surface 166of the forward mounting member 160. In one embodiment, the forwardmounting member 160 includes a length 302 (shown in FIGS. 63-70) definedalong the longitudinal axis 148, and the rear mounting member 200includes a length 304 defined along the longitudinal axis 148 that islonger than the length 302 of the forward mounting member 160.

Each rear mounting member 200 includes a plurality of fastener openingsextending through the rear planar mounting surface 204 that are sizedand shaped to receive a fastener such as, for example, a bolt to couplethe cradle frame 124 to the gearbox housing 118. Similar to the forwardmounting member 160, each rear support arm 202 includes an arcuate topsurface that extends between a top surface of the rear mounting member200 and a top surface of the rear member 142. The rear support arm 202also includes an arcuate outer surface and an arcuate inner surface. Thearcuate inner surface of the rear support arm 202 defines a gap 208between the rear mounting member 200 and the corresponding side memberouter surface 164 that sized and shaped to receive a portion of thegearbox housing 118 therein.

Referring to FIGS. 27-34, of the illustrated embodiment the top cover126 and the bottom cover 130 each include a plate 210 that includes anouter surface 212 and an inner surface 214 that extend between extendbetween a front endwall 216 and a rear endwall 218 along thelongitudinal axis 148, and between opposing side endwalls 220 along thetransverse axis 150. Each front endwall 216 includes an arcuate shapethat matches the arcuate shape of the inner surface of the forwardmember 140. The top cover 126 and the bottom cover 130 each include aplurality of fastening tabs 222 extend outwardly from the side endwalls220 and the rear endwall 218. Each fastening tab 222 includes an openingextending therethrough that is sized and shaped to receive fastener tofacilitate coupling the top cover 126 to the cradle frame 124.

The top portion 128 of the cradle frame 124 includes a top groove 224that is defined along a perimeter of the cavity 136 adjacent the cradleinner surface 134 that is sized and shaped to receive a portion of anouter edge of the top cover 126 such that the outer surface 212 of thetop cover 126 is positioned substantially flush with the top surface ofthe forward member 140, rear member 142, and side members 144, 146 ofthe cradle frame 124. A plurality of positioning slots 226 are definedalong the top surfaces of the rear member 142 and side members 144, 146.Each positioning slot 226 is sized and shaped to receive a correspondingfastening tab 222 therein. The top surfaces of the rear member 142 andside members 144, 146 include an opening defined within each positioningslot 226 to receive a fastener therein to facilitate coupling the topcover 126 to the cradle frame 124.

Similarly, the bottom portion 132 of the cradle frame 124 includes abottom groove 228 that is defined along a perimeter of the cavity 136adjacent the cradle inner surface 134 that is sized and shaped toreceive a portion of an outer edge of the bottom cover 130 such that theouter surface 212 of the bottom cover 130 is positioned substantiallyflush with the bottom surface of the forward member 140, rear member142, and side members 114, 146 of the cradle frame 124. A plurality ofpositioning slots 230 are defined along the bottom surfaces of the rearmember 142 and side members 144, 146 for receiving a correspondingfastening tab 222 therein. An opening is defined within each positioningslot 230 to receive a fastener therein to facilitate coupling the bottomcover 130 to the cradle frame 124.

The top cover 126 also includes a plurality of openings 232 extendingthrough the plate 210 and are sized and shaped to receive fastenerstherethrough to facilitate mounting the electrical inverter devices 108within the cradle chamber 138.

Referring to FIGS. 35-47 and 71-78, of the illustrated embodiment, thegearbox 116 includes the gearbox housing 118 and the gearbox cover 120.The gearbox housing 118 includes a body 234 having an inner surface 236and an outer surface 238. The inner surface 236 defines a gearbox cavity240 that is sized and shaped to receive the drive unit 26 therein. Theouter surface 238 extends between a front-side portion 242 and aback-side portion 244 along the transverse axis 150, and between aforward portion 246 and a rear portion 248 along the longitudinal axis148.

The front-side portion 242 of the gearbox housing 118 includes a firstmounting surface 250 positioned adjacent to the forward portion 246 anda second mounting surface 252 positioned adjacent to the rear portion248, as shown in FIG. 37. The first mounting surface 250 issubstantially planar that is compatible with the planar mounting surface166 of the forward mounting flange 158. The second mounting surface 252is substantially planar that is compatible with the planar mountingsurface of the rear mounting flange 204. The first mounting surface 250and the second mounting surface 252 each include a plurality of fasteneropenings extending through the gearbox housing 118 and are sized andshaped to receive corresponding fasteners to facilitate coupling thegearbox housing 118 to the cradle frame 124. In the illustratedembodiment, the forward mounting flange 158 is adapted to be coupled tothe gearbox housing 118 at the first mounting surface 250 adjacent tothe forward portion 246, and the rear mounting flange 198 is adapted tobe coupled to the gearbox housing 118 at the second mounting flange 252adjacent to the rear portion 248.

A shaft opening 256 extends through the back-side portion 244 and issized and shaped to receive the axle shaft 36 therethrough and includesa mounting surface 257 having apertures 259, as shown in FIG. 39.Mounting surface 257 is adapted to accept axle support 38 to be securedby fasteners. A motor opening 258 also extends through the back-sideportion 244 and is sized and shaped to receive a portion of the electricmotor 28.

In the illustrated embodiment, the forward portion 246 and the rearportion 248 by the gearbox housing 118 each includes a upper supportflange 260 and a lower support flange 262 that is spaced a distance fromthe upper support flange 260 along the vertical axis 174, as shown inFIG. 38. The upper support flange 260 and the lower support flange 262are configured to couple the gearbox housing 118 to a mount 18 extendingoutwardly from the gearbox housing 118 to facilitate coupling the axleassembly 10 to the vehicle. The forward portion 246 includes asuspension arm support flange 264 that is positioned above the uppersupport flange 260 along the vertical axis 174. The suspension armsupport flange 264 is adapted to couple a suspension arm 20 to thegearbox housing 118 and is orientated such that the suspension controlarm 20 extends outwardly from the gearbox housing 118 substantiallyparallel to the longitudinal axis 148.

The front-side portion 242 of the gearbox housing 118 also includes amounting shoulder 266 extending outwardly from an outer surface of thefront-side portion 242. The mounting shoulder 266 extends around aperimeter of the opening and includes a planar front surface 268. Aplurality of holes are defined along the front surface 268 for receivingcorresponding fasteners therein to facilitate coupling the gearbox cover120 to the gearbox housing 118.

The gearbox cover 120 includes a body 270 including an outer surface 272having a shape that substantially matches the shape of the mountingshoulder 266. The gearbox cover 120 includes a plurality of openings 274extending around a perimeter of the body 270 that are sized and shapedto received fasteners therethrough to facilitate coupling the gearboxcover 120 to the gearbox housing 118. The gearbox cover 120 is adaptedto be coupled to the gearbox housing 118 to enclose the drive unitwithin the gearbox cavity 240. The mounting shoulder 266 includes apositioning groove 276 defined along the front surface 268. The gearboxcover 120 includes a positioning lip that extends outwardly from asurface of the gearbox cover 120 and is configured to engage thepositioning groove 276 to facilitate coupling the gearbox cover 120 tothe gearbox housing 118.

In the illustrated embodiment, the mounting shoulder 266 extendsoutwardly a distance from the front-side portion 242 along thetransverse axis 150 such that the gearbox cover 120 is positioned withina gap 278 defined between the forward mounting flange 158 and thecorresponding rear mounting flange 198 when the gearbox 116 is mountedto the cradle frame 124.

In one embodiment, the axle assembly 10 may include a 700 mm walkthrough ultra-low floor (ULF) with a 275/70r22.5 Tire, 2 speed: −11.1:1;19.6:1, Axle Weight Rating of 11,600 kg, and 750,000 mile capable. Theaxle assembly 10 may also include a 1,000 mm walk through ULF with445/45r22.5 Tire, 2 speed: 11.1:1; 19.6:1, Axle Weight Rating of 10,500kg, and 750,000 mile capable. The axle assembly 10 may also include a580 mm walk through ULF with 305/70r22.5 Tire, 2 speed: 11.1:1; 19.6:1,Axle Weight Rating of 12,600 kg, and 750,000 mile capable. The axleassembly 10 may also include a 700 mm walk through ULF, One Speed,275/70r22.5 Tire, 1 speed: 15:1, Axle Weight Rating of 11,600 kg, and750,000 mile capable. The axle assembly 10 may also include a 1,000 mmwalk through ULF, One Speed with 275/70r22.5 Tire, 1 speed: 15:1, AxleWeight Rating of 10,500 kg, 750,000 mile capable. The axle assembly 10may also include a 580 mm walk through ULF, One Speed with 305/70r22.5Tire, 1 speed: 15:1, Axle Weight Rating of 12,600 kg, and 750,000 milecapable.

Referring to FIGS. 79-83, in another embodiment, the axle assembly 10utilizes a single electric motor 28 to drive all of the wheels 22coupled to the axle assembly 10. The axle assembly 10 includes a firstwheel drive unit 300 that permits the coupling of a first wheel assembly302, and a second wheel drive unit 304 that permits the coupling of asecond wheel assembly 306. The first wheel drive unit 300 and the secondwheel drive unit 304 may include some or all of the components of driveunit 26. In the embodiment shown, the axle assembly 10 is a dual wheelconfiguration with each wheel assembly 302, 306 including a pair ofwheels 22 coupled to each end of the axle assembly 10. The wheels 22defining axis of rotation 24.

In the illustrated embodiment, the axle assembly 10 includes a portalaxle 308 that is coupled between the first wheel drive unit 300 and thesecond wheel drive unit 304 for transferring torque generated by thefirst wheel drive unit 300 to the second wheel drive unit 304. Theportal axle 308 extends along a centerline axis 310 and is offset fromand spaced a distance 312 from the axis of rotation 24 along a verticalaxis 314. The portal axle 308 extends through or about the bridgesection 14 of the axle housing 12 between the opposing outer sections16. In the illustrated embodiment, the portal axle 308 is mounted to berotated by a first drop box 316 that is coupled to the first wheel driveunit 300. The portal axle 308 is adapted to engage a second drop box 318that is coupled to the second drive unit 304. The first and second dropboxes 316, 318 can be of any suitable configuration with any number ofgear reductions. The portal axle 308 includes a shaft rotatablysupported within or about the bridge section 14 with the shaft coupledto the first drop box 316 at one end and the second drop box 318 atanother end.

The first wheel drive unit 300 includes the electric motor 28 and adifferential 320 coupled to the electric motor 28, as shown in FIG. 80.A gear reduction is provided between the electric motor 28 and thedifferential 320 in a similar or the same manner as discussed aboverelative to the drive unit 26. A transmission 330, as described aboverelative to the drive unit 26, may also be incorporated between theelectric motor 28 and the differential 320. The differential 320transfers torque from the electric motor 28 to the hub assembly 32 ofthe first wheel drive unit 300 and is also coupled to the portal axle308 for transferring torque from the electric motor 28 through theportal axle 308 and to the hub assembly 32 of the second wheel driveunit 304. In other words, the portal axle 308 transfers torque from thefirst wheel drive unit 300 to the second wheel drive unit 304. It is tobe appreciated that the differential 320 is illustrated in FIGS. 81 and83 with certain components removed.

In one embodiment, as shown in FIGS. 80 and 81, each of the first 316and second 318 drop boxes have a single drop, which can be a gearreduction or can be a 1:1 drop. Preferably, the embodiment shown inFIGS. 80 and 81 does not incorporate a gear reduction across the portalaxle 308. In another embodiment, as shown in FIGS. 82 and 83, the first316 and second 318 drop boxes have different drops, with the first dropbox 316 having a single gear drop and the second drop box 318 having adouble gear drop. Each drop box 316 and 318 can have the same or adifferent gear reduction. Preferably, in the embodiment shown in FIGS.82 and 83, there is a gear reduction across the portal axle 308.Specifically, the second wheel drive unit 304 preferably includes a gearreduction 322 coupled to the second drop box 318 and the hub assembly 32at the second wheel drive unit 304. Additional details of a drop box andportal axle, components of which may be used in the present disclosure,are described in U.S. patent application Ser. No. 10/389,192 to Groveset al., now U.S. Pat. No. 6,964,317, filed Mar. 14, 2003, titled “DriveAssembly for a High Ground Clearance Vehicle”, which is incorporatedherein by reference in its entirety. Drop boxes include an input shaftthat drives an output shaft through a chain drive. The chain drive ofthe drop box includes an input sprocket, an intermediate sprocketassembly and an output sprocket. A first chain interconnects the inputsprocket and the intermediate sprocket assembly and a second chaininterconnects the intermediate sprocket assembly and the outputsprocket. While chains and sprockets are illustrated, gears may be usedinstead to transfer power from the differential 320 to the portal axle308.

As shown in FIGS. 80-83, the axle assembly 10 may include a singleelectric motor, two-speed configuration including a portal axle lengthbetween 700 mm and 1000 mm, a 1,000 mm or 700 mm walk through,445/70r22.5 or 275/70r22.5 Tire, 2 speed: 11.1:1; 22:1, Axle WeightRating of 10,500 kg to 11,600 kg, and 750,000 mile capability. The axleassembly 10 may include a single electric motor, one-speed configurationincluding a portal axle length between 700 mm and 1000 mm, a 1,000 mm or700 mm walk through, 445/70r22.5 or 275/70r22.5 Tire, 1 speed: 15:1,Axle Weight Rating of 10,500 kg to 11,600 kg, and 750,000 milecapability.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation. Manymodifications and variations of the present invention are possible inlight of the above teachings, and the invention may be practicedotherwise than as specifically described.

What is claimed is:
 1. An axle assembly comprising: an axle housingincluding a first gear box, a second gear box and a cradle assemblycoupling the first gear box to the second gear box; a first hub assemblyadapted to be rotated by the first gear box and a second hub assemblyadapted to be rotated by the second gear box, the hub assemblies forminga first axis of rotation; the first gearbox including an electric motorhaving an output shaft, a transmission mounted for rotation with theoutput shaft, a differential mounted for rotation with the transmissionand a first drop box having an input shaft mounted for rotation with thedifferential and having an output shaft; a portal axle mounted forrotation by the output shaft, the portal axle adapted to extend from thefirst gearbox to the second gear box, the portal axle forming a secondaxis of rotation that is offset from the first axis of rotation of thehub assemblies; and a second drop box having an input shaft mounted forrotation with the portal axle and an output shaft adapted to drive thesecond hub assembly.
 2. The axle assembly of claim 1, wherein the firstgearbox includes an axle shaft that is mounted for rotation with thedifferential.
 3. The axle assembly of claim 2, wherein each hub assemblyincludes a planetary gear set mounted for rotation with the axle shaft,wherein the planetary gear set increases torque to drive wheels coupledto the hub assemblies.
 4. The axle assembly of claim 3, wherein theplanetary gear set includes a planetary gear, a sun gear of theplanetary gear is coupled to the axle shaft, a planet carrier of theplanetary gear is coupled to a wheel hub, a ring gear of the planetarygear is coupled to a hub axle support and is held stationary withrespect to the planet carrier and the sun gear.
 5. The axle assembly ofclaim 1, further comprising an inverter assembly positioned within theaxle housing and coupled to the electric motor for providing electricalpower to the electric motor.
 6. The axle assembly of claim 1, whereinthe cradle assembly is offset from the first axis of rotation of the hubassemblies.
 7. The axle assembly of claim 6, wherein the cradle assemblyis formed to include an inner cavity.
 8. The axle assembly of claim 7,further comprising an inverter assembly positioned within the innercavity of the cradle assembly and coupled to the electric motor forproviding electrical power to the electric motor.
 9. The axle assemblyof claim 7, further comprising a cover member adapted to cover the innercavity of the cradle assembly.
 10. The axle assembly of claim 1, whereinthe first gearbox includes a gearbox housing and a gearbox coverremovably coupled to the gearbox housing, the cradle assembly is adaptedto be removably coupled to the gearbox housing.
 11. The axle assembly ofclaim 10, wherein the second gear box includes a second gearbox housingand a second gearbox cover removably coupled to the gearbox housing, thecradle assembly is adapted to be removably coupled to the second gearboxhousing.
 12. The axle assembly of claim 1, wherein the portal axleextends from the first gearbox through the cradle assembly to the secondgearbox.